Duloxetine hydrochloride is a potent dual reuptake inhibitor of serotonin and norepinephrine possessing comparable affinities in binding to serotonin and norepinephrine transport sites. Duloxetine hydrochloride has, therefore, been implicated in the treatment of various diseases related to these effects. For example, duloxetine hydrochloride is the active ingredient of the antidepressant drug Cymbalta®. It is also used to target pain related to diabetic neuropathy and stress urinary incontinence.
Preparation of duloxetine hydrochloride has been disclosed elsewhere, for example in U.S. Pat. No. 5,023,269. Crystalline forms of the free base of duloxetine and their preparation have been reported in WO 2005/108386. The amorphous form of duloxetine hydrochloride salt together with its preparation has been reported in WO 2005/019199.
There is no generally applicable method for preparing a crystalline form of an amorphous drug. For example, it is impossible to know without experimentation whether any crystalline form of a given compound exists. Even once it has been found that a drug can be crystallised, extensive experimentation is usually required before a repeatable and quantifiable process is identified from which the crystalline form can be isolated. In this respect, several independently variable conditions, such as the nature of solvent, concentration of solvent and temperature, must be correctly identified in order to elucidate a suitable process. Indeed, to date, there have been no reports describing isolation or production of crystalline duloxetine hydrochloride.
It is, therefore, an object of the present invention to provide crystalline forms of duloxetine hydrochloride together with methods for the production thereof.